1. Field of the Invention
This invention relates to helicopter rotor blades and more particularly to selectively shaped ramp tabs for use therewith to eliminate or reduce to within acceptable limits blade pitching moment dynamic unbalance and being bonded thereto so as to be totally within the blade chord dimension to avoid trailing edge damage.
2. Description of the Prior Art
In the fixed wing and rotary wing art, trailing edge trim tabs have been used to reduce rotor unbalance, however, all known types of trim tabs are either bolted or riveted to the blade as in Howard U.S. Pat. No. 2,656,132, and such a connection subjects the blade proper to risk of fatigue failure. Trim tabs have also been installed so as to extend rearwardly beyond the trailing edge of the blade, such as in Stulen et al. U.S. Pat. No. 2,951,542 or British Pat. No 1,150,123 to Young dated Apr. 30, 1969, or metallic trailing edge pockets of blades are selectively bent to shape at their trailing edges for balance purposes. Experience has shown that blade trailing edges so deformeed and trim tabs extending beyond the blade trailing edge are highly susceptible to damage during blade handling thereby throwing the blade out of balance. Pivotable aileron-type tabs have been used in helicopter blades, such as the Verhage et al. U.S. Pat. No. 2,757,745 and Stevens U.S. Pat. No. 2,994,384, however, these devices add the complication of requiring actuating mechanism with its attendant weight and mechanical failure possibilities. The trim tab in Prewitt et al. U.S. Pat. No. 2,961,053 is apparently also of the aileron type.